This invention relates to types of bicyclic nucleator compounds that provide highly versatile nucleation benefits for different thermoplastics. Such nucleator compounds provide very high peak crystallization temperatures and short crystallization cycle time for certain thermoplastic formulations with or without the presence of other calcium stearate and/or peroxide components within the same type of formulation. Furthermore, such inventive nucleator compounds exhibit very little, if any, fugitivity from such thermoplastic formulations thereby providing excellent processing characteristics as well as excellent nucleation capabilities for a variety of different thermoplastic resins, independent of the presence of different, potentially necessary, additives (such as calcium stearate). Thermoplastic compositions as well as thermoplastic additive packages comprising such inventive nucleator compounds are also contemplated within this invention.
All U.S. patents cited below are herein entirely incorporated by reference.
As used herein, the term xe2x80x9cthermoplasticxe2x80x9d is intended to mean a polymeric material that will melt upon exposure to sufficient heat but will retain its solidified state, but not prior shape without use of a mold or like article, upon sufficient cooling. Specifically, as well, such a term is intended solely to encompass polymers meeting such a broad definition that also exhibit either crystalline or semi-crystalline morphology upon cooling after melt-formation. Particular types of polymers contemplated within such a definition include, without limitation, polyolefins (such as polyethylene, polypropylene, polybutylene, and any combination thereof), polyamides (such as nylon), polyurethanes, polyesters (such as polyethylene terephthalate), and the like (as well as any combinations thereof).
Thermoplastics have been utilized in a variety of end-use applications, including storage containers, medical devices, food packages, plastic tubes and pipes, shelving units, and the like. Such base compositions, however, must exhibit certain physical characteristics in order to permit widespread use. Specifically within polyolefins, for example, uniformity in arrangement of crystals upon crystallization is a necessity to provide an effective, durable, and versatile polyolefin article. In order to achieve such desirable physical properties, it has been known that certain compounds and compositions provide nucleation sites for polyolefin crystal growth during molding or fabrication. Generally, compositions containing such nucleating compounds crystallize at a much faster rate than unnucleated polyolefin. Such crystallization at higher temperatures results in reduced fabrication cycle times and a variety of improvements in physical properties, such as, as one example, stiffness.
Such compounds and compositions that provide faster and or higher polymer crystallization temperatures are thus popularly known as nucleators. Such compounds are, as their name suggests, utilized to provide nucleation sites for crystal growth during cooling of a thermoplastic molten formulation. Generally, the presence of such nucleation sites results in a larger number of smaller crystals. As a result of the smaller crystals formed therein, clarification of the target thermoplastic may also be achieved, although excellent clarity is not always a result. The more uniform, and preferably smaller, the crystal size, the less light is scattered. In such a manner, the clarity of the thermoplastic article itself can be improved. Thus, thermoplastic nucleator compounds are very important to the thermoplastic industry in order to provide enhanced clarity, physical properties and/or faster processing.
As an example of one type of nucleator, dibenzylidene sorbitol derivative compounds are typical nucleator compounds, particularly for polypropylene end-products. Compounds such as 1,3-O-2,4-bis(3,4-dimethylbenzylidene) sorbitol, available from Milliken Chemical under the trade name Millad(copyright) 3988 (hereinafter referred to as 3,4-DMDBS), provide excellent nucleation characteristics for target polypropylenes and other polyolefins. Other well known compounds include sodium benzoate, sodium 2,2xe2x80x2-methylene-bis-(4,6-di-tert-butylphenyl) phosphate (from Asahi Denka Kogyo K.K., known as and hereinafter referred to as NA-11), aluminum bis[2,2xe2x80x2-methylene-bis-(4,6-di-tert-butylphenyl)phosphate] (also from Asahi Denka Kogyo K.K., which is understood to be known as and hereinafter referred to as NA-21), talc, and the like. Such compounds all impart high polyolefin crystallization temperatures; however, each also exhibits its own drawback for large-scale industrial applications.
Other acetals of sorbitol and xylitol are typical nucleators for polyolefins and other thermoplastics as well. Dibenzylidene sorbitol (DBS) was first disclosed in U.S. Pat. No. 4,016,118 by Hamada, et al. as effective nucleating and clarifying agents for polyolefin. Since then, large numbers of acetals of sorbitol and xylitol have been disclosed, including bis(p-methylbenzylidene) sorbitol (hereinafter referred to as 4-MDBS). Representative references of such other compounds include Mahaffey, Jr., U.S. Pat. No. 4,371,645 [di-acetals of sorbitol having at least one chlorine or bromine substituent].
As noted above, another example of the effective nucleating agents are the metal salts of organic acids. Wijga in U.S. Pat. Nos. 3,207,735, 3,207,736, and 3,207,738, and Wales in U.S. Pat. Nos. 3,207,737 and 3,207,739, suggest that aliphatic, cycloaliphatic, and aromatic carboxylic, dicarboxylic or higher polycarboxylic acids, and corresponding anhydrides and metal salts, are effective nucleating agents for polyolefin. They further state that benzoic acid type compounds, in particular sodium benzoate, are the best nucleating agents for their target polyolefins.
Another class of nucleating agents was suggested by Nakahara, et al. in U.S. Pat. No. 4,463,113, in which cyclic bis-phenol phosphates was disclosed as nucleating and clarifying agents for polyolefin resins, as well as U.S. Pat. No. 5,342,868 to Kimura, et al. Compounds that are based upon these technologies are marketed under the trade names NA-11 and NA-21, discussed above.
Furthermore, a certain class of bicyclic compounds, such as bicyclic dicarboxylic acid and salts, have been taught as polyolefin nucleating agents as well within Patent Cooperation Treaty Application WO 98/29494, 98/29495 and 98/29496, all assigned to Minnesota Mining and Manufacturing. The best working examples of this technology are embodied in disodium bicyclo[2.2.1]heptene dicarboxylate and camphanic acid.
The efficacy of nucleating agents is typically measured by the peak crystallization temperature of the polymer compositions containing such nucleating agents. A high polymer peak crystallization is indicative of high nucleation efficacy, which generally translates into fast processing cycle time and more desirable physical properties, such as stiffness/impact balance, etc., for the fabricated parts. Compounds mentioned above all impart relatively high polyolefin crystallization temperatures; however, each also exhibits its own drawback for large-scale industrial applications.
For example, it is very desirable that the effective nucleating compounds exhibit a very high peak crystallization temperature, for example, above 125xc2x0 C. within a test homopolymer polypropylene that, when unnucleated exhibits a number of different characteristics such as a density of about 0.9 g/cc, a melt flow of about 12 g/10 min, a Rockwell Hardness (R scale) of about 90, a tensile strength of about 4,931 psi, an elongation at yield of about 10%, a flexural modulus of about 203 ksi, an Izod impact strength of about 0.67 ft-lb/in, and a deflection temperature at 0.46 mPa of about 93xc2x0 (which provides a homopolymer exhibiting an isotacticity of between about 96 and 99%), wherein said peak crystallization temperature is measured by differential scanning calorimetry in accordance with ASTM Test Method D3417-99 modified to measure at heating and cooling rates of 20xc2x0 C./minute. Such a polypropylene homopolymer provides an effective test subject for this purpose due to the general uniformity of product available (and thus better uniformity in peak crystallization temperature, etc., results, therein for samples of such a thermoplastic), as well as the widespread use of such a thermoplastic. Of course, it should be well understood by the ordinarily skilled artisan that such a test homopolymer is not the only thermoplastic in which the inventive nucleating agent may be present; it is solely a test formulation in order to determine the highest peak crystallization temperature, etc., for certain inventive nucleating agents under certain conditions. Of the nucleating agents mentioned above, only camphanic acid exhibits such a high polymer peak crystallization temperature within such a test homopolymer propylene formulation. However, as shown in the comparative examples within this invention, camphanic acid exhibits very poor thermal stability, where it tends to vaporize and accumulate on the surface of plastic processing equipments during processing. This phenomenon is generally referred to as xe2x80x9cplate outxe2x80x9d within the plastics industry. The xe2x80x9cplate outxe2x80x9d effect of this additive make it impractical for any commercial use. Thus, the combination of very high polymer peak crystallization temperature (thus highly efficient nucleation) and a low degree of fugitivity (and thus high thermal stability and low plate-out characteristics) within the target polymers (e.g., preferably polyolefins such as polypropylene) is very desirable within the plastics industry, particularly where the peak crystallization temperature is measured above 126xc2x0 C. within a homopolymer polypropylene measured by differential scanning calorimetry at a rate of 20xc2x0 C./minute. So far, such a combination has not been provided within this intensively studied area of polymer nucleating agents.
Beyond high polymer crystallization temperature and low fugitivity, there are a number of other performance characteristics important for the practical use of such nucleating agents. For example, one of great interest is the compatibility of such compounds with different additives widely used within typical polyolefin (e.g., polypropylene, polyethylene, and the like) plastic articles. As noted previously, calcium stearate compatibility is particularly important. Unfortunately, most of the nucleator compounds noted above (such as sodium benzoate, NA-11, disodium bicyclo[2.2.1]heptene dicarboxylate) exhibit deleterious nucleating efficacy when present with such compounds within polyolefin articles. It is generally speculated that the calcium ion from the stearate transfers positions with the sodium ions of the nucleating agents, rendering the nucleating agents ineffective for their intended function. As a result, such compounds sometimes exhibit unwanted plate-out characteristics and overall reduced nucleation performance as measured, for example, by a decrease in crystallization temperature during and after polyolefin processing of greater than 2xc2x0 C. as compared to the peak crystallization temperature of the nucleated polymer with no calcium stearate present therein. In order to avoid combinations of these standard nucleators and calcium salts, other nonionic acid neutralizers, such as dihydrotalcite (DHT4-A), would be necessary for use in conjunction with such nucleators. Such a combination, however, has proven problematic in certain circumstances due to worsened aesthetic characteristics (e.g., higher haze), and certainly higher costs in comparison with standard calcium salts.
Other problems encountered with the standard nucleators noted above include inconsistent nucleation due to dispersion problems, resulting in stiffness and impact variation in the polyolefin article. Substantial uniformity in polyolefin production is highly desirable because it results in relatively uniform finished polyolefin articles. If the resultant article does not contain a well dispersed nucleating agent, the entire article itself may suffer from a lack of rigidity and low impact strength.
Furthermore, storage stability of nucleator compounds and compositions is another potential problem with thermoplastic nucleators and thus is of enormous importance. Since nucleator compounds are generally provided in powder or granular form to the polyolefin manufacturer, and since uniform small particles of nucleating agents are imperative to provide the requisite uniform dispersion and performance, such compounds must remain as small particles through storage. Certain nucleators, such as sodium benzoate, exhibit high degrees of hygroscopicity such that the powders made therefrom hydrate easily resulting in particulate agglomeration. Such agglomerated particles may require further milling or other processing for deagglomeration in order to achieve the desired uniform dispersion within the target thermoplastic. Furthermore, such unwanted agglomeration due to hydration may also cause feeding and/or handling problems for the user.
Some nucleating agents, such as certain DBS derivatives, exhibit certain practical deficiencies such as a tendency to plate-out at high processing temperatures. DBS derivatives, particularly where the aromatic rings are mono-substituted, show much improved thermal stability. However, such compounds also tend to exhibit undesirable migratory properties coupled with problematic organoleptic deficiencies within certain polyolefin articles. As a result, such compounds cannot be widely utilized in some important areas, such as within medical devices (e.g., syringes, and the like) and food packaging.
These noticeable problems have thus created a long-felt need in the plastics industry to provide such compounds that do not exhibit the aforementioned problems and provide excellent peak crystallization temperatures and low fugitivity for the target polyolefins themselves. To date, the best compounds for this purpose remain those noted above. To date, nucleators exhibiting exceptionally high peak crystallization temperatures, low fugitivity, low hygroscopicity, excellent thermal stability, and non-migratory properties within certain target polyolefins, and compatibility with most standard polyolefin additives (such as, most importantly, calcium stearate) have not been available to the plastics industry.
Therefore, an object of the invention is to provide a polyolefin nucleating agent that provides excellent high peak crystallization temperatures to polypropylene articles and formulations and also exhibits extremely low fugitivity (excellent thermal stability, low plate-out). A further object of the invention is to provide a nucleator compound and compositions thereof that exhibit excellent calcium stearate compatibility within target polyolefin articles and formulations. Also, the inventive compounds must exhibit excellent low hygroscopicity in order to accord an extremely good shelf-stable additive composition. Another objective of this invention is to provide a nucleating compound and composition that exhibits low migration once incorporated within polyolefin articles. Another objective of this invention is to provide a nucleating agent and composition that exhibits little or no foul taste and/or odor within polyolefin articles. Another object of the invention is to provide a nucleator compound that affects the crystallization process within the target polyolefin polymer in such a manner that the resultant lamellar structure is highly unique (extremely thick) in comparison with other nucleated polypropylene articles and formulations such that said polyolefin exhibits very high stiffness properties. Additionally, it is an object of this invention to provide a nucleator compound or composition that may be used in various polyolefin media for use in myriad end-uses.
Accordingly, this invention encompasses a nucleating agent which induces a peak crystallization temperature of at least 125xc2x0 C. (preferably, at least 125.5; more preferably, at least 126; still more preferably, at least 126.5; and most preferably at least 127; preferably such a temperature is as high as possible, up to the level of a self-nucleated test homopolymer polypropylene resin, such as at about 137-8xc2x0 C., with a high temperature of about 134xc2x0 C. most preferred) for a test homopolymer polypropylene formulation, wherein the unnucleated test homopolymer propylene exhibits a density of about 0.9 g/cc, a melt flow of about 12 g/10 min, a Rockwell Hardness (R scale) of about 90, a tensile strength of about 4,931 psi, an elongation at yield of about 10%, a flexural modulus of about 203 ksi, an Izod impact strength of about 0.67 ft-lb/in, and a deflection temperature at 0.46 mPa of about 93xc2x0, and wherein said formulation is extruded then molded into plaques having dimensions of about 51 mmxc3x9776 mmxc3x971.27 mm, wherein said peak crystallization temperature is measured by differential scanning calorimetry in accordance with a modified ASTM Test Method D3417-99 at heating and cooling rates of 20xc2x0 C./minute, and wherein said nucleating agent also exhibits no appreciable fugitivity from said test homopolymer polypropylene formulation during compounding of said test homopolymer polypropylene formulation.
Also encompassed within this invention is a nucleating agent which induces a crystallization half time (txc2xd) of at most 2.0 minutes in a test homopolymer polypropylene formulation, wherein the unnucleated test homopolymer propylene exhibits a density of about 0.9 g/cc, a melt flow of about 12 g/10 min, a Rockwell Hardness (R scale) of about 90, a tensile strength of about 4,931 psi, an elongation at yield of about 10%, a flexural modulus of about 203 ksi, an Izod impact strength of about 0.67 ft-lb/in, and a deflection temperature at 0.46 mPa of about 93xc2x0 C., and wherein said formulation is extruded then molded into plaques having dimensions of about 51 mmxc3x9776 mmxc3x971.27 mm, wherein said txc2xd is measured by differential scanning calorimetry at a constant crystallization temperature of about 140xc2x0 C., and wherein said nucleator also exhibits no appreciable fugitivity from said polypropylene formulation.
Additionally, this invention also encompasses a nucleating agent which induces a standard peak crystallization temperature of at least 123.5xc2x0 C. in a test homopolymer polypropylene formulation, wherein the unnucleated test homopolymer polypropylene exhibits a density of about 0.9 g/cc, a melt flow of about 12 g/10 min, a Rockwell Hardness (R scale) of about 90, a tensile strength of about 4,931 psi, an elongation at yield of about 10%, a flexural modulus of about 203 ksi, an Izod impact strength of about 0.67 ft-lb/in, and a deflection temperature at 0.46 mPa of about 93xc2x0 C., and wherein said formulation is extruded then molded into plaques having dimensions of about 51 mmxc3x9776 mmxc3x971.27 mm, wherein said peak crystallization temperature measured by differential scanning calorimetry in accordance with a modified ASTM Test Method D3417-99 at heating and cooling rates of 20xc2x0 C./minute and wherein said nucleating agent is present in at most 1500 ppm, wherein said polymer nucleator exhibits no appreciable fugitivity from said polypropylene formulation during compounding of said polypropylene, and wherein said nucleating agent induces said peak crystallization temperature in said polypropylene formulation when no calcium stearate is present, and wherein said nucleating agent induces a comparative peak crystallization temperature of at most 2xc2x0 C. lower than said standard peak crystallization for the same polypropylene formulation when at least 800 ppm of calcium stearate is present. Furthermore, such a compound exhibits a very low hygroscopicity as well.
Additionally, this invention encompasses a nucleating agent which produces an effective nucleation density of greater than 7xc3x97109 nuclei/cm3 at an isothermal crystallization temperature of about 148xc2x0 C. in a test homopolymer polypropylene formulation comprising said nucleating agent, wherein the unnucleated test homopolymer propylene exhibits a density of about 0.9 g/cc, a melt flow of about 12 g/10 min, a Rockwell Hardness (R scale) of about 90, a tensile strength of about 4,931 psi, an elongation at yield of about 10%, a flexural modulus of about 203 ksi, an Izod impact strength of about 0.67 ft-lb/in, and a deflection temperature at 0.46 mPa of about 93xc2x0, and wherein said formulation is extruded then molded into plaques having dimensions of about 51 mmxc3x9776 mmxc3x971.27 mm, and wherein said nucleating agent also exhibits no appreciable fugitivity from said test homopolymer polypropylene formulation during compounding of said test homopolymer polypropylene formulation comprising said nucleating agent.
Still further encompassed within this invention is a nucleating agent which exhibits a nucleation effectiveness factor (NEF) of greater than 0.06 in a test homopolymer polypropylene formulation having a density of about 0.9 g/cc, a melt flow of about 12 g/10 min, a Rockwell Hardness (R scale) of about 90, a tensile strength of about 4,931 psi, an elongation at yield of about 10%, a flexural modulus of about 203 ksi, an Izod impact strength of about 0.67 ft-lb/in, and a deflection temperature of 0.46 mPa at about 93xc2x0 C., wherein said formulation is extruded and then molded into plaques having dimensions of about 51 mmxc3x9776 mmxc3x971.27 mm.
It should also be well understood and appreciated by one of ordinary skill within this art that the inventive nucleating agent is defined above as performing to a certain degree within a test polymer formulation, and is not required to be a component within such a test polymer formulation. Thus, although such an inventive nucleating agent must perform to a certain level within a test homopolymer propylene, it may be present within any other type of polymer (such as a thermoplastic), including blends of polymers. The particular polymers within which such an inventive nucleating is effective and useful are listed below in greater detail.
The bicyclic compounds are defined as organic compounds that contain two or more rings wherein at least two of the said rings share at least two nonadjacent atoms.
Some particular, non-limiting examples of such novel nucleator compounds include the metal or organic salts of saturated [2.2.1]bicyclic dicarboxylates, and most preferably of these types of compounds conforming to Formula (I) 
wherein M1 and M2 are the same or different and are independently selected from the group consisting of metal or organic cations, and R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 are individually selected from the group consisting of hydrogen, C1-C9 alkyl, hydroxyl, C1 -C9 alkoxy, C1-C9 alkyleneoxy, amine, and C1-C9 alkylamine, halogen, phenyl, alkylphenyl, and geminal or vicinal C1-C9 carbocyclic. Preferably, the metal cations are selected from the group consisting of calcium, strontium, barium, magnesium, aluminum, silver, sodium, lithium, rubidium, potassium, and the like. Within that scope, group I and group II metal ions are generally preferred. Among the group I and II cations, sodium, potassium, calcium and strontium are preferred, wherein sodium and calcium are most preferred. Furthermore, the M1 and M2 groups may also be combined to form a single metal cation (such as calcium, strontium, barium, magnesium, aluminum, and the like). Although this invention encompasses all stereochemical configurations of such compounds, the cis configuration is preferred wherein cis-endo is the most preferred embodiment. The preferred embodiment polyolefin articles and additive compositions for polyolefin formulations comprising at least one of such compounds are also encompassed within this invention.
The term xe2x80x9cno appreciable fugitivityxe2x80x9d as used as one description within this invention is intended to encompass nucleators which exhibit very high heat stabilities (and thus very low plate-out) within test polypropylene formulations. Therefore, a weight loss of nucleator compound during a thermal stability test of at most 5% is encompassed within this term. Such thermal stability testing is described in greater detail below.
As noted above, in order to develop a proper polyolefin nucleator compound or composition for industrial applications, a number of important criteria need to be met. The inventive nucleating agents meet all of these important requirements very well. For instance, as discussed in greater detail below, these inventive salts provide excellent high peak crystallization temperatures in a variety of polyolefin formulations, particularly within random copolymer polypropylene (hereinafter RCP) and homopolymer polypropylene (hereinafter HP). As a result, such inventive salts provide excellent mechanical properties for polyolefin articles without the need for extra fillers and rigidifying additives, and desirable processing characteristics such as improved (shorter) cycle time. The salts also show much improved hygroscopicity comparing to prior art and thus granular or powder formulations of such a salt do not agglomerate or clump together. Lastly, such inventive salts do not interact deleteriously with calcium stearate additives.
Such properties are highly unexpected and unpredictable, particularly in view of the closest prior art, the WO 98/29494 reference discloses nucleation and clarification additives for polyolefin articles including unsaturated [2.2.1]dicarboxylate salts; however, there is no exemplification of a saturated dicarboxylate salt of this type. The closest embodiment within that art is identified as disodium bicyclo[2.2.1]heptene dicarboxylate. After intensive investigations, it has been determined that, quite unexpectedly, as discussed below in greater detail, the hydrogenation of such compounds provides vastly improved nucleation efficacy for the inventive compounds and within the inventive polyolefin compositions. It has now been found that the saturation of Diels-Alder reaction products to form dicarboxylate salts, and in particular, without intending to limit the scope of the invention, saturated bicyclic dicarboxylate salts, provide unforeseen benefits for polyolefin nucleation processes.
As indicated in Table 1, below, the peak crystallization temperatures provided target polyolefin articles with these inventive saturated compounds are from about 2.5 to about 5xc2x0 C. above that for the related unsaturated compounds. Such dramatic improvements are simply unexpected and are unpredictable from any known empirical or theoretical considerations. Furthermore, significant improvements in hygroscopicity of the saturated compounds were also unexpectedly observed. Such unpredictable improvements are of great practical significance as discussed before.
Yet another surprise was the improved compatibility between these inventive saturated compounds and typical acid scavenger salt compounds utilized within polyolefin formulations and articles, such as calcium and lithium stearate. Such compatibility, coupled with the high peak crystallization temperatures available from the inventive compounds, thus provides a highly desirable thermoplastic nucleator compound. Furthermore, the ability to provide extremely high nucleation density measurements (above an order of magnitude than typical nucleating agents at various isothermal crystallization temperatures) is highly desirable and previously unattainable as well.
The inventive salts are thus added within the target polyolefin in an amount from about 50 ppm to about 20,000 ppm by weight in order to provide the aforementioned beneficial characteristics, most preferably from about 200 to about 4000 ppm. Higher levels, e.g., 50% or more by weight, may also be used in a masterbatch formulation. Optional additives within the inventive salt-containing composition, or within the final polyolefin article made therewith, may include plasticizers, antistatic agents, stabilizers, ultraviolet absorbers, and other similar standard polyolefin thermoplastic additives. Other additives may also be present within this composition, most notably antioxidants, antistatic compounds, antimicrobials (preferably silver-based ion-exchange compounds, such as ALPHASAN(copyright) antimicrobials available from Milliken and Company), perfumes, chlorine scavengers, and the like. Such additives, and others not listed, are well known to those skilled in the art.
The term polyolefin or polyolefin resin is intended to encompass any materials comprised of at least one polyolefin compound. Preferred examples include isotactic and syndiotactic polypropylene, polyethylene, poly(4-methyl)pentene, polybutylene, and any blends or copolymers thereof, whether high or low density in composition. The polyolefin polymers of the present invention may include aliphatic polyolefins and copolymers made from at least one aliphatic olefin and one or more ethylenically unsaturated co-monomers. Generally, the co-monomers, if present, will be provided in a minor amount, e.g., about 10 percent or less or even about 5 percent or less, based upon the weight of the polyolefin (e.g. random copolymer polypropylene), but copolymers containing up to 25% or more of the co-monomer (e.g., impact copolymers) are also envisaged. Other polymers or rubber (such as EPDM or EPR) may also be compounded with the polyolefin to obtain the aforementioned characteristics. Such co-monomers may serve to assist in clarity improvement of the polyolefin, or they may function to improve other properties of the polymer. Other examples include acrylic acid and vinyl acetate, etc. Examples of olefin polymers whose transparency can be improved conveniently according to the present invention are polymers and copolymers of aliphatic monoolefins containing 2 to about 6 carbon atoms which have an average molecular weight of from about 10,000 to about 2,000,000, preferably from about 30,000 to about 300,000, such as, without limitation, polyethylene, linear low density polyethylene, isotactic polypropylene, syndiotactic polypropylene, crystalline ethylene propylene copolymer, poly(1-butene), polymethylpentene, 1-hexene, 1-octene, and vinyl cyclohexane. The polyolefins of the present invention may be described as basically linear, regular polymers that may optionally contain side chains such as are found, for instance, in conventional low density polyethylene.
Although polyolefins are preferred, the nucleating agents of the present invention are not restricted to polyolefins, and may also give beneficial nucleation properties to polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), as well as polyamides such as Nylon 6, Nylon 6,6, and others. Generally, any thermoplastic composition having some crystalline content may be improved with the nucleating agents of the present invention.
The compositions of the present invention may be obtained by adding the inventive saturated bicyclic dicarboxylic salt (or combination of salts or composition comprising such salts) to the thermoplastic polymer or copolymer and merely mixing the resultant composition by any suitable means. Alternatively, a concentrate containing as much as about 20 percent by weight of the inventive saturated [2.2.1] salt in a polyolefin masterbatch comprising the required acid scavenger may be prepared and be subsequently mixed with the target resin. Furthermore, the inventive compositions (with other additives potentially) may be present in any type of standard thermoplastic (e.g., polyolefin, most preferably) additive form, including, without limitation, powder, prill, agglomerate, liquid suspension, and the like, particularly comprising dispersion aids such as polyolefin (e.g., polyethylene) waxes, stearate esters of glycerin, montan waxes, mineral oil, and the like. Basically, any form may be exhibited by such a combination or composition including such combination made from blending, agglomeration, compaction, and/or extrusion.
The composition may then be processed and fabricated by any number of different techniques, including, without limitation, injection molding, injection blow molding, injection stretch blow molding, injection rotational molding, extrusion, extrusion blow molding, sheet extrusion, film extrusion, cast film extrusion, foam extrusion, thermoforming (such as into films, blown-films, biaxially oriented films), thin wall injection molding, and the like into a fabricated article.
Examples of particularly preferred fluid dispersions within the scope of the present invention are presented below.
Production of Inventive Salts